Bandwidth cap
Encyclopedia
A bandwidth cap, also known as a bit cap, limits the transfer of a specified amount of data
over a period of time. Internet service provider
s commonly apply a cap when a channel intended to be shared by many users becomes overloaded, or may be overloaded, by a few users. Implementation of a bandwidth
cap is sometimes termed a Fair Access Policy or Usage-based billing.
, Internet radio
or streaming video, a few users who use the connection at high rates for hours at a time may seriously impair the service of others. The concept is more relevant in cable internet
where both the core network
and the access network
are shared, than in DSL
where the core network is shared but the access network is not. It is most relevant in wireless internet, particularly satellite internet, where both the core network
and the access network
are shared and total network bandwidth is relatively narrow.
One type of bandwidth cap, administered by an Internet service provider
(ISP), simply limits the bitrate
or speed of data transfer on a broadband Internet connection. The purpose of bandwidth capping is to prevent individual users from consuming the entire transmission capacity of the cable, a shared resource. Critics have charged that it is a method to charge consumers more by introducing tiered bandwidth caps.
Capping might be handled by the user's cable modem
. Knowledge of capping has led to attempts
at uncapping
. When uncapping succeeds, the resulting data transfer rate is supposed to be extremely fast, but users who are caught are said to be banned permanently by broadband ISPs. Uncapping is considered theft of service by ISP's.
Sophistication is possible, and even required in limiting bandwidth. The simplest approach simply limits the data rate. The problem with the simplest approach is, a very active user could consume the maximum bandwidth continuously, theoretically imposing an excess burden on the ISP and possibly reducing the performance of other users.
Channel capacity
is a finite resource, using huge amounts of it can be deemed an abuse in countries with poor communications infrastructure. Dial-up ISPs often published policies that tried to clarify the difference between "unmetered" and "unlimited".
A more sophisticated approach is called "bursting", the administrator would specify a "peak rate limit", a lower "sustained rate limit", and a "credit limit". If you continuously saturate your connection, you will only get the sustained rate. While you are idle or use less than the sustained rate, you accumulate a credit, in bytes, up to some limit. If you try to saturate your connection after idling, you will get the peak rate until your credit runs out, at which point you will again be running at the sustained rate limit. The transition from peak rate to sustained rate could be abrupt, gradual, or even an arbitrarily designed curve. If you alternately idle and saturate, your long-term average data rate will never exceed the sustained rate limit, and your short-term data rate will never exceed the peak rate limit. This is known as a Token bucket
.
Other schemes or models are possible to regulate bursting. Running at the peak rate could accumulate a debt. Once the debt reaches a limit, the user is held to the sustained rate limit and the debt does not change. Only running below the sustained limit (or idle time) pays back the debt. The behavior is similar.
" tend to use upstream bandwidth heavily, and violate most service agreements. (Cable and other broadband services tend to be asymmetrical, making upstream capacity scarcer than downstream.) Somehow the ISP detects that the user is an offender — perhaps by analyzing traffic to detect the activity of a server, or perhaps by comparing the user's long-term data rate against an unpublished limit. If a user gets tagged as an offender, then the ISP imposes a lower bandwidth cap upon that user, and/or restricts other services. e.g. NTT Communications in Japan imposes a 30GB/day upload cap with a warning for a first violation and disconnection for repeat offenders.
The implementation of a sustained rate limit might appear as a reduced cap. If the data rate improves automatically after idle time, this would confirm the operation of a sustained rate limit.
Reports claim that the intervention of an administrator is required to remove a lowered cap.
Many broadband
Internet Service Providers in North America
and Europe
introduced bandwidth caps in the early 2000's. The same practice has been in place in Australia
, New Zealand
, Malaysia and South Africa
since the release of broadband. Data caps on internet in New Zealand
result from many popular websites being hosted in the United States, hence local ISPs must lease international capacity; a proponent of a second international cable to the United States claims that cheaper international capacity will result in ISPs raising their data caps.
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
over a period of time. Internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
s commonly apply a cap when a channel intended to be shared by many users becomes overloaded, or may be overloaded, by a few users. Implementation of a bandwidth
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
cap is sometimes termed a Fair Access Policy or Usage-based billing.
Standard cap
In many situations, each user of a network is expected to use high speed transmission for only a short time, for example to download a megabyte web page in less than a second. When use is continuous, as it might be in the case of file sharingFile sharing
File sharing is the practice of distributing or providing access to digitally stored information, such as computer programs, multimedia , documents, or electronic books. It may be implemented through a variety of ways...
, Internet radio
Internet radio
Internet radio is an audio service transmitted via the Internet...
or streaming video, a few users who use the connection at high rates for hours at a time may seriously impair the service of others. The concept is more relevant in cable internet
Cable internet
In telecommunications, cable Internet access, often shortened to cable Internet or simply cable, is a form of broadband Internet access that uses the cable television infrastructure. Like digital subscriber line and fiber to the premises services, cable Internet access provides network edge...
where both the core network
Core network
A core network, or network core, is the central part of a telecommunication network that provides various services to customers who are connected by the access network. One of the main functions is to route telephone calls across the PSTN....
and the access network
Access network
An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...
are shared, than in DSL
Asymmetric Digital Subscriber Line
Asymmetric digital subscriber line is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice...
where the core network is shared but the access network is not. It is most relevant in wireless internet, particularly satellite internet, where both the core network
Core network
A core network, or network core, is the central part of a telecommunication network that provides various services to customers who are connected by the access network. One of the main functions is to route telephone calls across the PSTN....
and the access network
Access network
An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...
are shared and total network bandwidth is relatively narrow.
One type of bandwidth cap, administered by an Internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
(ISP), simply limits the bitrate
Bitrate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
or speed of data transfer on a broadband Internet connection. The purpose of bandwidth capping is to prevent individual users from consuming the entire transmission capacity of the cable, a shared resource. Critics have charged that it is a method to charge consumers more by introducing tiered bandwidth caps.
Capping might be handled by the user's cable modem
Cable modem
A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...
. Knowledge of capping has led to attempts
Hacker (computer security)
In computer security and everyday language, a hacker is someone who breaks into computers and computer networks. Hackers may be motivated by a multitude of reasons, including profit, protest, or because of the challenge...
at uncapping
Uncapping
Uncapping, in the context of cable modems, refers to a number of activities performed to alter one's internet service provider modem settings. It is sometimes done for the sake of bandwidth Uncapping, in the context of cable modems, refers to a number of activities performed to alter one's internet...
. When uncapping succeeds, the resulting data transfer rate is supposed to be extremely fast, but users who are caught are said to be banned permanently by broadband ISPs. Uncapping is considered theft of service by ISP's.
Sophistication is possible, and even required in limiting bandwidth. The simplest approach simply limits the data rate. The problem with the simplest approach is, a very active user could consume the maximum bandwidth continuously, theoretically imposing an excess burden on the ISP and possibly reducing the performance of other users.
Channel capacity
Channel capacity
In electrical engineering, computer science and information theory, channel capacity is the tightest upper bound on the amount of information that can be reliably transmitted over a communications channel...
is a finite resource, using huge amounts of it can be deemed an abuse in countries with poor communications infrastructure. Dial-up ISPs often published policies that tried to clarify the difference between "unmetered" and "unlimited".
A more sophisticated approach is called "bursting", the administrator would specify a "peak rate limit", a lower "sustained rate limit", and a "credit limit". If you continuously saturate your connection, you will only get the sustained rate. While you are idle or use less than the sustained rate, you accumulate a credit, in bytes, up to some limit. If you try to saturate your connection after idling, you will get the peak rate until your credit runs out, at which point you will again be running at the sustained rate limit. The transition from peak rate to sustained rate could be abrupt, gradual, or even an arbitrarily designed curve. If you alternately idle and saturate, your long-term average data rate will never exceed the sustained rate limit, and your short-term data rate will never exceed the peak rate limit. This is known as a Token bucket
Token bucket
The token bucket is an algorithm used in packet switched computer networks and telecommunications networks to check that data transmissions conform to defined limits on bandwidth and burstiness ....
.
Other schemes or models are possible to regulate bursting. Running at the peak rate could accumulate a debt. Once the debt reaches a limit, the user is held to the sustained rate limit and the debt does not change. Only running below the sustained limit (or idle time) pays back the debt. The behavior is similar.
Lowered cap
Another type of capping refers to the reported phenomenon of an ISP reducing an individual user's bandwidth cap, without notifying that user, as a defensive measure and/or as a punishment for heavy use, especially for upstream traffic. "ServersServer (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
" tend to use upstream bandwidth heavily, and violate most service agreements. (Cable and other broadband services tend to be asymmetrical, making upstream capacity scarcer than downstream.) Somehow the ISP detects that the user is an offender — perhaps by analyzing traffic to detect the activity of a server, or perhaps by comparing the user's long-term data rate against an unpublished limit. If a user gets tagged as an offender, then the ISP imposes a lower bandwidth cap upon that user, and/or restricts other services. e.g. NTT Communications in Japan imposes a 30GB/day upload cap with a warning for a first violation and disconnection for repeat offenders.
The implementation of a sustained rate limit might appear as a reduced cap. If the data rate improves automatically after idle time, this would confirm the operation of a sustained rate limit.
Reports claim that the intervention of an administrator is required to remove a lowered cap.
Many broadband
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
Internet Service Providers in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
introduced bandwidth caps in the early 2000's. The same practice has been in place in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, Malaysia and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
since the release of broadband. Data caps on internet in New Zealand
Internet in New Zealand
In New Zealand the major telephone company, Telecom New Zealand, owns the majority of the infrastructure and is the only provider of digital subscriber lines , which they wholesale to their subsidiary Xtra , as well as many of Telecom's "competitors", with varying speeds and download...
result from many popular websites being hosted in the United States, hence local ISPs must lease international capacity; a proponent of a second international cable to the United States claims that cheaper international capacity will result in ISPs raising their data caps.
Download quota
A download quota is a restriction fixed by some ISPs to limit the volume of data downloaded by the end user during a fixed period, usually a month. Once a fixed download cap (e.g. 250 gigabytes/month) has been reached by the end user, the speed at which they access the internet is usually throttled to a slower speed, cut off, or they are charged for excess data usage.See also
- Bandwidth hoggingBandwidth hoggingA bandwidth hog is a derogatory term for a user of an internet connection who uses more bandwidth than other users on the network. ISPs now refer to bandwidth hogs as heavy users in an attempt to avoid backlash by the public....
- Bandwidth managementBandwidth managementBandwidth management is the process of measuring and controlling the communications on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance of the network.- Management :Bandwidth management mechanisms may be...
- Bandwidth throttlingBandwidth throttlingBandwidth throttling is a reactive measure employed in communication networks to regulate network traffic and minimize bandwidth congestion. Bandwidth throttling can occur at different locations on the network. On a local area network , a sysadmin may employ bandwidth throttling to help limit...
- Usage Based Billing (UBB)